Influenza Hemagglutinin (HA) Protein Structure

Q1: Structure of Influenza

Influenza Viruses is a viral infection of the respiratory and pulmonary system generally accompanied by fever. It is hard to prevent influenza because it is contracted simply by the act of breathing. There are necleopretein, P protein and RNA in the center of a influenza virus and the center domain is surrounded by capsid and lipid envelope from inside to outside. On the surface of influenza, there are Hemagglutinin (HA) and Neuraminidase (NA), both of which serve as antigenic proteins. In a word, the influenza virus is composed of a lipid bilayer with hemagglutinin and neuraminidase attached to it.

Q2: Structure of Hemagglutinin (HA)

Hemagglutinin (HA) is a glycoprotein that binds the virus to the cell being infected. The hemagglutinin molecule is actually a combination of three identical proteins (shown here as gray, green, and purple) that are bound together to form an elongated cylindrical shape. Hemagglutinin consists of a globular head and a stem. The globular head consists of three chains, Chains A, C, and E. The stem of the protein consists of three chains as well, Chains B, D, and F. The head of the protein has been noted to vary in structure and function where the stem, or glycan, has been noted to be more conserved in structure and function. The function of chains A, C, and E is the binding of influenza to pulmonary cells and the start of endocytosis.

Q3: Structure of Neuraminidase (NA)

Neuraminidase (NA)is an enzyme that helps the virus to breach cell walls. Neuraminidase is also known as sialidase because it breaks the linkages between sialic acid and cellular glycoproteins and glycolipids found in cell walls. Neuraminidase forms mushroom-like projections on the surface of the influenza virus. The top consists of four identical proteins with a roughly spherical shape. The picture below shows how each of these subunits is rotated by 90 degrees relative to the center of the arrangement.